A differential assembly of the type contemplated for the present invention is generally of the design shown in U.S. Pat. No. 2,859,641 (GLEASMAN). That patent is incorporated herein by reference to the extent necessary to provide specific details of the structure of the differential assembly.
This type of differential includes a rotatable gear housing, a pair of drive axles received in bores formed in the sides of the housing, and a differential gear arrangement mounted within a main body portion of the housing for driving the axles. One end of the main housing body includes a flange for mounting a ring gear or other means providing power input to the differential from the vehicle's drive shaft. The other end of the gear housing is provided with a cap which may be either formed as an integral part of the main housing body or may be removably secured to the housing.
Within this prior art differential is a gear arrangement which is referred to as a "crossed-axis compound planetary gear complex". This arrangement includes (a) a pair of helical-worm side gears coupled to each axle end, and (b) one or more so-called "transfer" gears associated with each of the side gears, the transfer gears being in mesh with each other for transferring and dividing torque between the axle ends. The transfer gears are mounted in pairs within slots, or windows, formed in the main body portion of the gear housing; and each transfer gear of a pair rotates on an axis of rotation that is substantially perpendicular to the axis of rotation of the side gears and gear housing.
The transfer gears are in reality "combination" gears, i.e., the middle portion of each gear constitutes a worm-wheel portion while the outer ends of the gear are formed with integral gear teeth of either spur or helical design, these outer ends being referred to hereinafter simply as "spur-gear" portions. The gear arrangement is such that, for each pair of combination gears: the worm-wheel portion of a first combination gear meshes with one side gear, while the worm-wheel portion of the other combination gear meshes with the other side gear, and the spur-gear portions of each of the respective combination gears mesh with each other.
The combination gears are each mounted to the gear housing body by a pin which fits into a pair of axially aligned bores in the housing. Usually, two or three pairs of combination gears are mounted in the same assembly, being positioned at equidistant spacings around the two side gears. Thus, each side gear is intermeshed with two or three combination gears, and the individual combination gears of each combination-gear pair intermesh with each other. In this manner, the driving loads between the two axles are, ideally, divided equally between the different sets of combination-gear pairs. To achieve such load balancing, considerable care is taken during manufacture of the differential assemblies to assure that all of these gears are accurately positioned relative to each other. In this regard, it is of particular importance that the spur-gear portions at the ends of each combination-gear pair be in mesh.
Nonetheless, slight positional variations do occur in both manufacture and assembly, and these can sometimes result in minor misalignments in which the combination-gear pairs are not properly meshed with their respective side gears and/or with each other. Optimally, where three pairs of combination gears are positioned about the side gears, the loads experienced by each side gear are evenly divided between the worm-wheel portions of each of its three related combination gears; and, similarly, the load experienced by the worm-wheel portion of each combination gear is shared nearly equally between its two spur-gear portions. However, the minor misalignments just mentioned above can jeopardize this optimal balancing of the side gear load and can cause sufficient load imbalance to produce undesirable wear and/or noise problems.
My invention facilitates the correction of such minor misalignments and, thereby, helps reduce such load imbalance problems.